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Oncoceratium n. gen. is proposed to accommodate Oncoceratium amphidactylum n. gen. n. sp. (Monogenoidea, Gyrodactylidae). Although the proposed genus is monotypic, the differences presented in the diagnosis clearly establish it as distinct from species from other genera, such as Gyrodactylus von Nordmann, 1832 and especially those that occur exclusively in the Neotropical region. The new genus is diagnosed by the presence of a bulbous male copulatory organ, with one row of spinelets of similar sizes and shapes, while the only spine usually found in the gyrodactylids is absent or not differentiated; a haptor with anchors presenting points folded outwards, and superficial and deep roots continuous and indistinguishable; the absence of a deep bar; and hooks in two bilateral clusters of eight hooks. Oncoceratium amphidactylum n. gen. n. sp. is described from the tamboatá fish, Hoplosternum littorale (Hancock) (Callichthyidae), and is characterized by the presence of a pair of horn-shaped anchors with the point turned outwards, a superficial bar shield and absent deep bar, hooks disposed in bilateral lobes, and a MCO with no spine or with a row with large spinelets visible in place of the spine. In addition to the morphological features, distance analysis and Bayesian inference, based on 5.8s and partial ITS2, support placing the new species in a new genus, and not including it in a cluster of species of Gyrodactylus and near to Gyrodactyloides bychowskii Albova, 1948, Ieredactylus rivuli Schelkle et al., 2011 and Laminiscus gussevi (Bychowsky & Polyansky, 1953) Pálsson & Beverely-Burton, 1983., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Henneguya guanduensis was originally described as a gill parasite of the Hoplosternum litoralle, a siluriform fish belonging to the Callichthyidae family. A study was undertaken with 58 specimens of H. litoralle taken from Batalha River in the state of São Paulo. The fish were collected and examined searching for lesions and/or myxosporean plasmodia. The prevalence of infection was 9.31% in the gills and 5.17% in the intestine. The mature spores had elongated bodies with polar capsules of inequal size and a caudal length greater than body length. Morphological characteristics identified the parasite as H. guanduensis. Molecular analysis of the SSU rDNA partials sequences resulted in a 1796 bp and 1712 bp for gills and intestine repectively, demonstrating significant genetic differences with previously described species of Henneguya and 99.7% similarity to each other when aligned. Phylogenetic analysis comparing the SSU rDNA sequence of H. guanduensis with closest species as indicated by BLASTn Max Score showed H. guanduensis as sister species of H. loretoensis in a subclade compose by species that parasites fishes from Amazon basin. This is the first report of the finding of Henneguya guanduensis spores in the intestine of Hoplosternum littorale., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Studies on the production of Pimelodidae catfish in the Amazon are generally carried out in large fishing centers. However, the data referring to small-scale fisheries have gaps that can represent a risk to the activity. This study evaluated the volume produced and the revenue obtained from migratory catfish of the Pimelodidae family of commercial interest landed in Humaitá, Amazonas, Brazil, from May 2018 to April 2019. Daily monitoring was carried out with the Z-31 Fishermen's Colony through questionnaires to fishermen for each vessel docked. The total production was 6013.93 kg, with 1,689 fish counted and 13 species. A total of 186 landings by 122 fishermen in 24 fishing sites characterized as rivers, lakes, and "igarapés" were evaluated. The average selling price was R$5.57/kg, and the highest volumes were obtained from July to September, mainly with gillnets, where the "Surubim" Pseudoplatystoma punticfer had the highest volume and revenue. Low productivity was verified in most localities, characterizing the fishing as artisanal. The lack of adequate conditions for storing and transporting fish, the local hydrological variations, and the presence of hydroelectric plants on the Madeira River are major factors limiting the fishing expansion in southern Amazonas. [ABSTRACT FROM AUTHOR]